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Thread: T43 Acadia Transmission Tuning for TCC locking and Unlocking

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    Default T43 Acadia Transmission Tuning for TCC locking and Unlocking

    I have a 2008 Acadia, which I rebuilt the engine. In testing it out, I've found the TCC locking and unlocking constantly at mid throttle and cruise. On moderate acceleration, once it hits 3rd gear, it almost feels like it is bucking it is locking and unlocking so much. I've confirmed that it is the locking and unlocking by disabling it all together, then it shifts and drives beautifully. I've done a lot of research and found a lot of people having the same problem with cameros and solving it by increasing the lock pressure or pwm percentage using hptuners. But I don't have that option with efilive. I've also seen where people use a different TCM OS and that has fixed the problem. But I don't see anywhere or anyhow to do that.

    I don't have hptuners and have never used it. I've used efilive to change transmission tuning on a 2004 Chevy Express (made it feel like I doubled the engine HP, and increased mileage), on my 2006 2500 duramax, on my brothers 2005 2500 duramax, on my dad's 2008 6.0l gas, and now this 2008 Acadia. Every one has turned out great, increasing the mileage, making it feel more powerful, and making it more enjoyable to drive. The acadia felt very underpowered to begin with, but is good now. I tried changing the desired slip to 0. I also tried changing the TCC ramp pressure, but only a little. I increased the whole table 50% which didn't change most of the table much, everything was low numbers to begin with. Then upped the numbers in low slip (5-40 rpm) to 5-17 kpa/s where stock was 0-10 kpa/s. It appears that this is a table showing desired rate of pressure increase, rather than applied pressure, so I left 0 rpm slip at 0 kpa/s. This appears to have only made it lock and unlock faster and more aggressively. I disabled the TCC in all but 6th gear in normal mode, and my shift points keep it out of 6th gear until over 65mph. I am using tow mode and the tap shift to check how my changes are affecting the TCC lockup.

    Has anyone been able to fix this problem through efilive? Is there a way I could try another TCM OS?

    One last thing is, I bought this vehicle with the timing problem at 191,000 miles. Body and interior were in good shape, so I spent a pretty penny rebuilding the engine and replacing all the wear parts (brakes, struts, etc) hoping that it would be good for a long time to come. But I never drove it before I did all the work. I did flush the transmission as soon as the car was back in one piece, then it got a fluid change after 1 hour of running, then it got another fluid change when I pulled the engine back out to fix a rod bearing after it spun with 200 miles on it. Flush and first change were using AcDelco Synthetic Dex VI, but this final fill I went with Amsoil Signature Dex VI. Now I've got another 200 miles on it and this appears to be the last problem left. I can not guarantee that it is not a physical problem with the TC, but I would bet that it isn't based on everything I've seen, felt, and heard.
    2006 K2500 CC LB LBZ Diesel

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    Lifetime Member Tre-Cool's Avatar
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    what os does the current trans have?

    GM did some wierd/stupid shit with the trans calibrations across the years. I had similar problem with a 2010 holden t43 tune, switched to a camaro cal & locked up worked as it should.

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    Currently the OS is 24249042. Switching to a camero OS is one thing I've heard working for others, just not specifically for an Acadia. Is that possible for me to try? How would I go about doing it, if it were possible?

    After doing some checking, the only option hptuners has for an 08 acadia that efilive does not, is specifying min TCC applied pressure and specifying what the transmissions TCC valve pressure ratio is (which would multiply the entire range of TCC applied pressures if changed).

    There are two possible things happening. Either 1. it is commanding the TCC to unlock for some unknown reason, such as other parameters not being met to stay locked or whatever. Which would be a programming issue, and a different OS or factory change in programming would be needed to fix it. It could also be some internal malfunction that is only presenting itself when the TCC is locked. In that case I really don't have enough information to find the problem, nor know how to find the information and am thus screwed.

    Or option 2. it is not being commanded to unlock, but rather is slipping so much it feels like it is unlocked. If it is actually dropping the pressure so much it has effectively unlocked, then specifying a min lock pressure would fix the problem. Looking at other cars applied pressure tables (which I don't have access to for the acadia and hptuners doesn't either) I see that the lock pressure can be very minimal (less than 20 psi) at times. If my TCC is worn and after locking the TCM drops the pressure to it's set point of 20psi (or similar) and that isn't enough for mine to hold, it would feel like it is unlocking. Then the TCM senses the slip, adjusts pressure accordingly, which makes the TCC grab again and starts the cycle over. That would cause a never ending cycle of locking and unlocking. I've timed it, it only acts locked for 0.5 sec to 2 seconds at a time. If the TCM were adjusting pressure real time and learning, that is what I would expect to see happen. But it may not be learning enough to stop it from happening. Say the max it is allowed to learn for pressure offset is 10psi, and mine requires 20psi above original programming to stay locked, the learned pressure would never be enough to keep it locked, but would vary the time it stayed locked. In this case, hptuners could be used to fix my problem. I just don't want to spend $3-400 on a guess. Also it could be the camero OS and calibration has a much higher TCC applied pressure anticipating people driving a camero more aggressively than an suv. And thus fixing this problem as well, which would logically make more sense, but without more knowledge of the system I couldn't know which was the case.

    I know I have a tendency to get too deep into the why of things. Back when I worked on Cars, then Trucks for a living, it helped me to be the top diagnostic tech at the shop. But I've been out of practice for 12 years and lost a lot in that time. It does sometimes help to talk these things out, and I've not kept in touch with anyone who has any understanding of how these things work, so this is as close as I get.

    Everything would fit with it not intentionally unlocking, but dropping pressure too much causing slippage. So if I don't come up with any better ideas, I will have to pursue the problem from that stand point. I would prefer to test that theory without spending more money, so if anyone knows how I could try a camero OS and calibrations please let me know.
    2006 K2500 CC LB LBZ Diesel

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    If I'm reading the T43 sticky on changing the OS, then any of these OSs should work for me.

    24244551,24249042,24253414,24249179,24251030,24249 833

    And one person said that 21249179 should be give the most options. So is there anyone with a 21249179 OS willing to post theirs and I can try to figure out how to use it? Or where how could I go about trying to flash that OS into my TCM?
    2006 K2500 CC LB LBZ Diesel

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    Lifetime Member Tre-Cool's Avatar
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    i did some testing yesterday with loading in a 24256025 tune into a tcm that was originally a 24256125 with HPT as efilive says it's incompatible.

    The only reason i did it, is because people had used my tune with the 6025 to fix up the convertor lock up issue into newer model tcm's. So I'm now unsure how the compatible calibrations come about.

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    Forum tyhee Site Admin GMPX's Avatar
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    It is all based on the year model the controller software was released. Usually a transition between year models is when GM make the big changes that can cause problems.
    And by problems I mean like the Commodore 12633016 into a 12624402, you aren't coming out of that experience with a smile

    So we just have in the background a check to compare the software year releases, sometimes they might be compatible, others will end in disaster.
    Need official EFILive help, please go here.
    For tuning support please post your questions on this forum (or other auto forums).
    Sorry if I don't respond to your PM, don't take it personal.


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    Lifetime Member Tre-Cool's Avatar
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    Quote Originally Posted by GMPX View Post
    It is all based on the year model the controller software was released. Usually a transition between year models is when GM make the big changes that can cause problems.
    And by problems I mean like the Commodore 12633016 into a 12624402, you aren't coming out of that experience with a smile

    So we just have in the background a check to compare the software year releases, sometimes they might be compatible, others will end in disaster.
    yeah i havent really had any concerns with the pro-active safety's. I know HPT tends to give no fcks, which why so many people corrupt the ecu's.

    i thought for shits and giggles I would give it a shot while diagnosing a conversion i have been working on. E40 + PCS Controller & 6L80.

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    I found a tuning file with OS 21249179 from a Camero. I don't see anywhere to change the TCC applied pressure in it. In fact I don't see any more options than I have with my factory OS.
    I believe I am going to attempt to swap all of my original calibrations into that tune. Then I'll plug in the spare TCM I have, and try to read that tune to see what is there, and see if it could be flashed with this tune. If it is one that shows compatible, I will attempt to flash PCM OS & Calibrations. I am not sure if that is the correct way to go about it, but with the other TCM plugged in, it shouldn't hurt the one on the vehicle, Right?

    I seem to remember the Flash PCM OS being grayed out before. I'll need to hook up the computer again to check, but if it is why would it be? Would that mean it is not capable of flashing the OS?

    If it doesn't work on the other TCM I have, would it be safe to try to flash the one on the vehicle? With the safety measure in place, Efilive shouldn't let me do it if it would wreck my TCM, Right?
    2006 K2500 CC LB LBZ Diesel

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    I was reading through the tuning manual, and found where it says efilive personal version can not be used to change an OS. I've had my V2 for about 8 years, I think, but I would assume it would be a personal version. Does that mean that I can't flash a new OS into the car, or am I miss interpreting?
    2006 K2500 CC LB LBZ Diesel

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    Efilive version 7 full flash was grayed out, but it looked like it would work in v8. The other TCM I have is a different os all together, so it won't work to flash one of these to it. It is the original TCM that was in this transmission, and one thought was to change the VIN and swap it back into the trans to try. But it wasn't a lot of fun to swap it out while everything was together.

    Anyway I tried a full test flash of the TCM in the vehicle using V8. It said flash successful. I even did a read before testing it out, and everything looked good. Tried a test drive, and it stayed in 1st or 2nd gear (hard to tell which when the speedo was wrong), no shifting. It only had 1 forward gear and reverse. So something wasn't right and I did a full flash back to my latest mod that worked with the original os. Tested, everything worked like it had before. So it isn't any worse than before, but no better. The camero tcm tune did not help.

    As a side note I did swap all the calibrations over, piece by piece, which was a pain because the tables didn't line up. They went to a much higher torque and higher slippages, etc. And after all that my speedo went nuts. I hit a speed limiter at 108mph while traveling around 30mph. Must be some difference between FWD and RWD tuning.
    2006 K2500 CC LB LBZ Diesel

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